private void btSearch_Click(object sender, EventArgs e)
{
List <EL.HangHoa> listHangHoa = hangHoaBUS.Search(new EL.HangHoa(tbMaHang.Text, tbTenHang.Text, tbNoiChua.Text, tbSLHang.Text, tbGiaHang.Text));
dataTable.Rows.Clear();
foreach (EL.HangHoa hanghoa in listHangHoa)
{
dataTable.Rows.Add(hanghoa.MaHang, hanghoa.TenHang, hanghoa.NoiChua, hanghoa.SoLuongHang, hanghoa.GiaHang);
}
dataGridView1.DataSource = dataTable;
}